The present invention relates generally to the field of laboratory test slides, and specifically to the use of patterned ceramic indicia as a labeling means for substrates used to immobilize biomolecules.
High density arrays are new tools used by drug researchers and geneticists which provide information on the expression of genes from particular cells. A high density array typically comprises between 5,000 and 50,000 probes in the form of DNA strands, each of known and different sequence, arranged in a determined pattern on a substrate. The substrate may be any size but typically takes the form of a 1xc3x973 inch glass microscope slide.
The arrays are used to determine whether target sequences interact or hybridize with any of the probes on the array. After exposing the array to target sequences under selected test conditions, scanning devices can examine each location in the array and determine whether a target molecule has hybridized with the probe at that location. DNA arrays can be used to study which genes are xe2x80x9cturned onxe2x80x9d or up-regulated and which genes are xe2x80x9cturned offxe2x80x9d or down-regulated. So for example, a researcher can compare a normal colon cell with a malignant colon cell and thereby determine which genes are being expressed or not expressed only in the aberrant cell. The regulation of these genes serves as key targets for drug therapy.
In order to immobilize the probe sequence to the substrate, a coating is applied to the slide to enhance the attachment. One common film that is applied for this purpose is gamma aminopropyltriethoxylsilane (GAPS). After such a coating is applied, the DNA is printed onto the substrate surface by any number of printing methods including piezoelectric, typo pin printing, capillary pin printing, ink jet printing, etc. The end result is an array with spots of immobilized probes at a pitch of between 10-500 xcexcm.
A means for linking the physical slide and the vast amount of genetic information contained on it, to a corresponding database which stores information about each of the thousands of sequences contained on the slide, is required. This link takes the form of a bar code label, for example. In order to meet a market demand for pre-coated GAPS slides for use by customers to print their own arrays, the Assignee of the present invention prepared a product for market. Applicants affixed adhesive bar code labels to the surface of the coated slides and stored them at various conditions as a test in preparation for product release.
It was discovered that the GAPS coated slides having the bar-code labels were becoming progressively less effective at immobilizing DNA probes over time, while non-labeled slides remained effective. This discovery led to focused study on the effects of the labeling on the chemistry of the GAPS coating. After some study, it became clear that the chemical adhesive from the bar code label was deleteriously affecting the GAPS surface film. The present invention solves the problem caused with adhesive labels by providing a chemically inert labeling system for substrates designed to immobilize biomolecules.
This invention provides a labeling format for use in assays that require the immobilization of biomolecules on a flat substrate surface. The ceramic labeling indicia of the present invention provide a format that can supply the user with required identification about the substrate and its content without adversely affecting a chemically active surface required for probe immobilization.